Dylan & Peak Torque explore cycling suspension & cognitive dissonance

Locking out your shock does not improve cycling efficiency. Now, my sanity rebels at that notion, but that’s what Dylan found. Peak Torque, in all his geeky engineering glory, knew immediately that this could not be true. (it just can’t!) So Peak Torque took it upon himself to absolutely 100% confirm Dylan’s findings. :smiley:

It’s a finding so contrary to collective colloquial cycling belief that it almost feels like a grand internet conspiracy. Especially if you have an expensive remote lock out device for your shock, I’ll bet it sounds like absolute codswallop. The more money you spend to do something the less likely you are to believe that something accomplishes nothing.

Personally, this information gives me so much cognitive dissonance that I’m almost suffering from vertigo.

Back in the day one of my club mates bought some expensive new dual-sided power meter pedals. I was super excited because that meant we could test the relative efficiency of different cranksets. To set the envelope we tested a dura ace 170mm crank against a $138 carbon crank I bought off Ali Express. I could reverse the left-side crank arm of the Chinese crank, put the heels of my hands on the end of the crank arms, and legit flex them more than 10mm. It was the floppiest crankset ever.

No measurable difference between those two cranksets. Not for a 5 minute effort. Not for a sprint. Not for a 20 minute effort. No measurable difference.

I still think we screwed the data up somehow. :wink: And I still rec spending the extra cash to get dura ace.

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So…

My slightly flexy, handcrafted and utterly beautiful Columbus Spirit steel frame is just as fast as any other high end carbon fiber frameset?

Yay! Although that’s one less excuse on the list for not being faster. :pensive:

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This got posted and discussed briefly in the XC Race bike thread a bit ago.

I think it’s good to have a dedicated thread to make it easier to find and continue discussion.

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Well, probably not. But if that gorgeous frame isn’t as fast as some carbon frame it is much more likely due to the aerodynamic performance of the tubes.

But, just to put your mind at ease, I once intimated to my club mates that I was going to attempt a national championship race on a super flexy titanium bike…I would say the room was evenly divided between people who didn’t think I could do well and people who were absolutely certain I wouldn’t do well. I was a relatively big rider on a flexy bike racing on the hilliest route in the RAAM qualifying bucket. All good arguments but in the end I set the course record, qualified for RAAM on a course nobody ever had (in my division) and won a national championship. So sometimes ya just gotta pedal it out and see what happens.

And I think it’s a real advantage to get into an aero position, put your head down, and let the rhythmic swaying of your bottom bracket going back-and-forth hypnotize you for hours on end.

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Nonsense…next thing you know you are gonna try and tell me that 700x28 road tires with substantially less pressure are more efficient than my 700x19’s jacked up to 150 psi…or that some fancy carbon wheels are faster than my ultra-lightweight tubular wheels.

Insanity across the board.

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I don’t have anything to add but that I really really love when science or experimentation disproves conventional knowledge. It makes life seem like there is still mystery out there and it may be in the everyday things that we just know

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Me thinks your methodology is flawed.

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This test indicated that mechanically the bike may not be less efficient locked or not. Which is interesting no doubt. However, unfortunately bikes don’t ride themselves and I’m still under the belief that the rider is less efficient. There’s likely a greater metabolic cost unlocked versus locked and this test doesn’t solve anything for me. If I’m doing a MTB 100 the metabolic cost is everything but at 1-2 hour events it likely means little.

I imagine it all comes down to marginal gains. Like cutting grams off your bike weight to go up hills faster. I like the unlocked versus locked debate and I hope it leads to something.

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Peak Torque makes a super important point about the metabolic cost to maintain the same output over different suspension settings here (and seated v. standing). The elevated HR on the standing runs is an important distinction to make. I think there’s also a case to be made for the adage, “feeling fast is fast”

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No doubt…and Dylan acknowledged that in the closing of his video. it is also one of the reasons you see seasoned pros favoring lightweight bikes in the climbing stages of major races…because it “feels” fast and there can be a psychological edge to that feeling.

One important point however is that both the first study Dylan mentioned, and his own tests, were tapped out at 250w. Intuitively, it would seem that substantially higher watts could bring suspension-induced drivetrain losses into play. And 250w is not a huge number…I reckon most everyone here can hold 250w for a few minutes on any climb. What happens at 350-400w? Definitely worth some follow-up, I think. (Note - I have only watched Dylan’s video at this point and not the second one, so maybe they cover that).

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The biggest take away from me with this is that suspension/pedalling efficiency can’t be measured as easily as we might like. There is certainly energy loss going on in any suspended bike, I really appreciate the fact he took the time to quickly address the function of the damper - what I think we can extrapolate from these tests is that the energy loss in a suspension system isn’t enough to slow the bike given a (near) constant power output. How that translates to trails, or even a gravel or fire road climb will be much much harder to measure and execute.

At the end of the day we’re still going to chase lightweight and efficient pedaling bikes (in the context of XC/Trail). Fun stuff to think about never-the-less!

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Pretty sure that it is addressed in Dylan’s video. Both from him comparing all the studies done by others, and also in his own testing, where he was looking at differences in HR for the efforts, as well as time and power.
I think he hit the nail on the head when he talked about “feeling fast” versus being fast! Like 120 psi in road tires feels fast, but is in fact slow.

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Except in this case, it is a wash. Locking out the suspension isn’t slower…but it isn’t any faster, either. With 120psi tires, it is, in fact, slower.

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I interpreted this differently. By upstream and downstream, what I gather was the reason why the times were the same is because the power impacting the drivetrain was the same. Same power/Same time. Time wasn’t affected because power wasn’t affected. The issue was upstream, more effort was being exerted by the rider to generate the same power, meaning the energy loss was felt by the rider, not the pedal power meter. 300 watts in the pedal was really 320? watts to the rider in the form of rider efficiency, not drivetrain efficiency.

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Right. Because in this case, locking out or not may not matter.

It is undoubtedly true that whenever a shock/fork is compressing, kinetic energy is lost to heat generation/friction and so on.

What is not clear, is if that vertical force compressing the suspension would otherwise contribute to forward motion of the bike. Maybe that force is just absorbed in deformation of tires in a rigid bike?

This is just my n=1. But I for sure feel a lot more fresh, and less fatigued if I do the same trails on my full suspension versus my HT. So I would very much hope Dylan’s correct :stuck_out_tongue:

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Good point. That the damper certainly absorbs some of the pedaling energy intended to drive the bike forward is an aside, not the main point to be drawn in this case. (the cost of output). Power at the pedals, is power at the pedals.

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If the theory is that the wasted energy with an unlocked suspension goes into the shocks, it seems like this is something that could be measured directly. Energy being dissipated by the shock will result in heating up the shock, which could be measured directly. At least for some rear shocks, the shock is fairly well isolated, and could have some insulation added to reduce heat loss to the environment. Certainly for longer efforts any substantial energy loss should result in measurable temperature change. I would think that even 5-10 watts over 10s of minutes would be easily measurable with a little insulation on the shock.
Also, another way to look at this would be to put the bike on a test fixture that compressed and released the shock at a similar rate/displacement to pedaling and to measure the heat dissipated in that situation to set some bounds on how much energy is lost in the shock.
This doesn’t account for the energy dissipated by the rider’s body due to movement or vibration, which as I understand it is thought to be a significant part of the system inefficiency in high pressure tires on rough roads. Shocks could in theory reduce this loss off-road similarly to how lower pressure tires help on the road.
I think these experiments are interesting, and provide evidence that the bicycle mechanical system likely isn’t less efficient in locked vs unlocked state, at least under the conditions tested. That doesn’t fully answer the question of the whole bike + rider system, but is interesting nonetheless.

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I don’t think anyone is arguing that energy is being dissipated in the fork & shock. That’s what they are designed to do.
I think the question is, would that “wasted” energy otherwise “go through the cranks” and help propel the bike forward? That is not necessarily the case. That energy could otherwise be “wasted” on increased contact pressure at the tires, causing deformation of tires etc

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I think it is likely that your time to exhaustion will be shorter with the suspension open vs closed - effectively pulling your power duration curve downwards.

Do any of the current power meter pedal systems allow you to look at non-tangential forces? That is probably the key to this.

Mike

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Obviously the times are going to be identical if the power to the cranks is identical. The issue is that putting that same power to the crank is harder because you’re losing energy to the shocks as heat.